1. Field of Invention
The invention relates to a blade roll, preferably for the manufacture of letter envelope blanks as more particularly set forth herein.
2. The Prior Art
A blade roll of this type is known from DE 33 02 038 to the same applicant. It serves for cutting out window openings in blanks of window letter envelopes. In connection with this blade roll, a foil blade of the type similar to a printing plate is mounted on a punching roll and held there by purely mechanical means. The foil blade, which is chamfered at its ends, is suspended on a carrier part, and clamped and tensioned at its trailing end by means of holding and tensioning means. The blades always must have a defined length between their fastening elements, and require precisely executed chamfers. Furthermore, the mounting or exchanging of a foil blade requires substantial time expenditure.
It is also known according to applicant""s DE 198 41 834.5 to arrange foil blades on a blade roll. The foil blade is fixed in this connection with a chamfered front end in a slot of the roll with the help of a clamping strip. The remaining part of the foil blade is held on the periphery of a blade cylinder by means of magnetic force, the cylinder being structured in the form of a dish. The manufacture of the roll slot and clamping strip as well as of the chamfer of the foil blade requires high precision and labor expenditure. Furthermore, the clamping strip has to be removed and installed with each blade exchange.
EP 0 312 422 B1 discloses a rotating cutting device in connection with which a foil blade for punching out window openings is held on the periphery of a dish-like blade cylinder by magnetic force alone. For positioning a foil blade on the blade cylinder, the leading edge of the foil blade is fixed and aligned on a strip slightly projecting beyond the periphery of the cylinder. The cutting device does in fact permit quick positioning and fixing of a foil blade on the blade cylinder; however, it has the drawback that the foil blade can get displaced on the blade cylinder under unfavorable cutting conditions, or even may get destroyed in the worst case. Therefore, cutting is possible with the blade roll against a jointly rotating counter roll, but no cutting is possible against a stationary counter bar.
The invention is concerned with the problem of designing a blade roll in particular for the manufacture of letter envelopes so that foil blades arranged on its roll jacket can be quickly exchanged and positioned and fixed with adequate accuracy.
The problem is solved according to the invention by arranging holding and positioning pins in a row in the roll body part. The pins radially project from the peripheral surface with a height (h) approximately corresponding with a thickness (d1) of the base plate. In a front zone adjoining the leading edge, the base plate has a number of slots aligned in one alignment with the cutting edge. The width (b) of the slots corresponds with the width (b1) of the holding and positioning pins projecting into the slots. In this way, the foil blade can be axially displaced and repositioned within the range of a slot length (d5), but is fixed and reproducibly positioned in the peripheral direction of the roll body part. Additional features of the invention are set forth below in association with the description and the drawing.
The invention has the particular advantage that the foil blades can be quickly and comfortably positioned and replaced on the blade roll. The foil blades are held here on the peripheral surface of the blade roll both positively by the holding and positioning pins engaging the slots of the base plate, and retained there non-positively by magnetic holding forces. Also, it is advantageous that the foil blade can be displaced axially parallel on the blade roll as the holding and positioning pins are being inserted into the slots. A variable axially parallel positioning of the foil blade is possible in connection with a slightly asymmetric arrangement of the holding and positioning pins on a strip. Another advantage is that the blade roll as defined by the invention can use conventional foil blades of the type described in the parallel application DE 198 41 834.5, with angularly chamfered leading ends and clamping strips adapted to such ends.